1. Field of the Invention
This invention relates to new and improved auto-sequential commutated controlled current inverters having a new and improved reset circuit. The inverters are of the type for supplying current of a controlled magnitude to a multi-phase load such as a three-phase alternating current induction motor. In such arrangements, the current inverter is switched at a desired operating frequency for the load being supplied. In the example cited, the inverter switching frequency determines the speed of rotation of the induction motor.
More specifically, the invention relates to new and improved auto-sequential commutated controlled current inverter having a new and improved reset circuit wherein the reset circuit facilitates transfer of load current from one phase of a multi-phase load to another phase through the medium of the inverter while automatically commutating off the branch of the inverter circuit which had been supplying a previously excited phase.
2. Prior Art Problem
Auto-sequential commutated controlled current inverter circuits having reset circuits have been used in the past and are presently available to the industry. The use of reset circuits with controlled current inverters of this type provides two advantageous operating features. The first advantage is that the reset circuit achieves the transfer of current flow from one phase to another in a minimum amount of time, thus allowing higher frequency operation. The second advantageous feature is that the time of transfer from one phase to another is made substantially independent of the load operating point. However, known controlled current inverter reset circuits are designed in a manner such that the commutating capacitors employed in such inverters have to accomodate not only the load current (which requirement is inherent in the design of auto-sequentialcommutated controlled current inverters) but also must withstand added voltage stresses due to the reset currents. This characeristic of known reset circuit designs results in the need for larger power rated components as well as increases in the stresses placed on such components during operation. To overcome this problem, the present inventon was devised.